1. Field of the Invention
The present invention relates to a dielectric porcelain composition having a low-temperature sintering behavior capable of using a low-melting-point conductive material, such as Ag/Cu, as internal wiring and an electronic component using the dielectric porcelain composition.
2. Description of the Related Art
In mobile communications with cellular phones or the like, a high-frequency band of several hundred MHz to several GHz, which is called a “quasi microwave band”, is used. Thus, high-frequency characteristics are emphasized in electronic components, such as resonators, filters, and capacitors, that are used in mobile communication devices.
As for such electronic components, a dielectric porcelain composition having a desired dielectric constant of 30 to 60 at frequencies used and a low dielectric loss may be required depending on their purposes. For the evaluation of a dielectric loss, for example, a quality factor indicated by the factor Qf, which is the product of Q=1/tan δ and a resonance frequency f, is used the lower the dielectric loss, the larger the quality factor Qf. The dielectric loss means a power loss of a high-frequency component, so a dielectric porcelain composition having a large quality factor Qf is required.
As a dielectric material having a dielectric constant of 30 to 60 and a low dielectric loss, many materials composed of BaO—TiO2 ceramics as a major component have been proposed. However, in a case of proposed BaO—TiO2 ceramics, the sintering temperature is as high as over 1000° C., so that even when an internal electrode having a high electrical conductivity, such as Ag/Cu, is formed on a BaO—TiO2 ceramic substrate and laminated with multiple layers, there is a problem of difficulty in co-firing. Thus, to produce a multifunctional substrate using a low-melting-point conductive material, such as Ag/Cu, in an internal electrode thereof by co-firing, it is necessary to reduce the firing temperature to, for example, about 900° C.
Japanese Laid-open Patent Publication No. 05-325641 discloses a technology for achieving low-temperature firing while maintaining high-frequency characteristics by a combination of BaO—TiO2 ceramics as a major component and, as a minor component, at least B2O3 or glass containing B2O3 as one of glass ingredients.
An electronic component, such as a filter, using this kind of dielectric porcelain composition is usually mounted on a resin substrate by soldering. In this case, as the resin substrate, an FR4-grade copper-clad laminate is generally used. In a case of an FR4-grade resin substrate, a linear thermal expansion coefficient of its material is about 13 ppm/° C. However, in conventional technologies as disclosed in Japanese Laid-open Patent Publication No. 05-325641 and the like, a linear expansion coefficient of a dielectric porcelain composition that an electronic component mounted on a resin substrate has is not specifically considered. In the conventional technology disclosed in Japanese Laid-open Patent Publication No. 05-325641, a linear expansion coefficient of a dielectric porcelain composition is, for example, lower than 9 ppm/° C., and differs from a linear thermal expansion coefficient of a resin substrate. As a result, under the condition of high temperature, a difference in expansion between the resin substrate and the dielectric porcelain composition side may occur due to the difference in linear thermal expansion coefficient between the two.